In order to understand the influence of electrical discharges on combustion ignition processes, a wire-to-wire spark created in an air/methane mixture has been studied. The electron temperature and density of this spark discharge have been determined. Voltage, current measurements, photography and optical emission spectroscopy have been used to characterize this discharge as a function of time, pressure and equivalence ratio. The size and shape of the phenomenon were observed using photography. Voltage and current measurement were correlated to these photos to determine the time scale of the discharge and the propagating flame. The Boltzmann plot method was applied to the results of time-resolved spectroscopy during the discharge phase and yielded to the electron temperature the first 10 μs. Finally, from Stark broadening of Hα, Hβ and copper lines, the electron density of the plasma was deduced for the first 10 μs, with values up to 1018 cm−3. These data will be used as the initial condition in a numerical simulation.